For testicular cancer diagnosis, Bölükbaşi et al. developed an electrochemical AFP immunosensor combining Fe3O4 NPs@COF/AuNPs electrodes with a dual-shell magnetic nanoparticle signal amplifier (MNPs@SiO2@TiO2), achieving ultra-sensitive detection of AFP with a detection limit of 3.30 fg/mL (Fig. 10F) [305]. The gene discussed is AFP; the disease is testicular cancer.